Drying mill for wet granular particles

ABSTRACT

A method and means for preventing the clogging of fluid energy type drying mills caused by accumulation of recycled particles, which comprises deflecting a stream of hot inlet gases at one portion of the mill to disperse the accumulated recycled particles and propel them into the path of the circulating gaseous stream.

United States Patent 11 1 1111 3,927,479

Stephanoff Dec. 23, 1975 DRYING MILL FOR WET GRANULAR 2,237,091 4/1941 Stephanoff 34/57 E PARTICLES 2,297,726 10/1942 Stephanoff..... 34/10 2,502,916 4/1950 Bar 34/57 E [75] Inventor: Nicholas N. Stephanoff, Haverford,

[73] Assignee: Fluid Energy Processing &

Equipment Co., Hatfield, Pa.

[22] Filed: Nov. 26, 1974 [21] Appl. No.: 527,251

[52] US. Cl. 34/57 E; 34/57 R [51] Int. Cl. F26B 17/00; F26B 17/10 [58] Field of Search 34/10, 57 R, 57 B, 57 E [56] References Cited UNITED STATES PATENTS 1,478,526 l2/l923 Merrell 34/10 Primary Examiner-John J Camby Attorney, Agent, or Firm--Arthur A. Jacobs, Esq.

[57] ABSTRACT A method and means for preventing the clogging of fluid energy type drying mills caused by accumulation of recycled particles, which comprises deflecting a stream of hot inlet gases at one portion of the mill to disperse the accumulated recycled particles and propel them into the path of the circulating gaseous stream.

3 Claims, 3 Drawing Figures US. Patent Dec. 23, 1975 3,927,479

mill. This type of. mill is disclosed in applicants U.S.v

Pat. No. 3,329,418 which is incorporated herein by reference.

Although the above-described patented mill operates in a most satisfactory manner for many materials, it has been found that when the material being dried is relatively coarse, containing relatively large, lumpy particles, the wetter particles that are centrifugally returned through the downstack accumulate on the walls of the lower portion of the upstack where they become agglomerated and deteriorated.

When the operation of the mill is halted for any reason, the above-mentioned agglomerated material slides down into the inlet chamber behind the last downstream gas inlet nozzle. When the mill is re-started, this accumulated material tends to melt under the heat of the hot gases, and this melted material clogs the mill. Furthermore, if the accumulated material is of the combustible type, it may even catch fire. In any event, this agglomerated material, when intermixed with the finished product passing through the mill, not only contaminates this finished product but also necessitates frequent shut-down of the mill in order that it may be cleaned out.

The above-described action of the centrifugally returned particles is further pronounced because of the manner in which the hot gases enter the inlet chamber. In this respect, although the nozzles are tangentially disposed relative to the axis of the inlet chamber, the actual inlet openings themselves are in the plane of the floor of the inlet chamber, so that even though the initial direction of the gases, as they pass through the noules below the floor, is tangentially directed toward the upstack, when they actually pass through the openings themselves, the circumferential rims of the openings have a tendency to deflect them at an upward angle from the nozzle axis so that there are two vector forces acting on the gases. This is generally desirable because it aids to more thoroughly suspend the particles in the hot gases while still permitting the particles and gases to flow toward the upstack due not only to the vector forces produced by the initial tangential direction of the gases through the nozzles in the floor but to the axial direction of the gases propelled into the inlet chamber by the nozzle at the front end of the inlet chamber. However, this flow upwardly from the floor nozzles even further enhances the accumulation of the recycled wet particles in the upstack because the flow from these nozzles decreases the actual velocity of the axial flow of the gases and particles toward the upstack and increases the tendency of the particles to accumulate behind the last downstream nozzle due to the formation of the back eddy behind this nozzle.

It is, therefore, one object of the present invention to overcome the above-described difficulties by providing 2 an improvement in a drying mill wherein the. recycled wet particles are prevented from clogging the mill behind the last downstream gas inlet nozzle.

.Another object of the present invention is to provide an improvement of the aforesaid type which is simple and inexpensive to install and maintain and which does not, otherwise,-interfere with the most effective operation of the mill. 1

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following description when read in conjunction with the accompanying drawings wherein:

FIG. 1 is a sectional view of a portion of a drying mill embodying the present invention.

FIG. 2 is a modified form of the last downstream nozzle used in the mill of FIG. 1.

FIG. 3 is another modified form of the last downstream nozzle. I

Referring now in greater detail to the figures of the drawing, there is shown in FIG. 1 the bottom portion of the drying mill, including the inlet chamber and its associated parts and the lowerportions of the upstack -and downstack. The upper portion of the mill includes a classifier section which joins the upstack and downstack to form a generally arcuate or doughnut-shaped structure and an exhaust port leading from the inner circumference of the mill between the classification section and downstack, all as shown in the aforesaid US. Pat. No. 3,329,418. However, since this upper portion forms no part of the present invention, by itself, it has not been shown in the drawing.

As shown in FIG. 1, the mill, generally designated 10, comprises an inlet chamber 12 having a front end in which is positioned agas inlet nozzle 14 connected to a source of hot gas such as a manifold or a combustion chamber (not shown). The nozzle 14 is arranged so that it projects a stream of hot gas, such as hot air, steam, or the like, in a straight axial direction through the inlet chamber 12.

On the bottom wall, or floor, of the inlet chamber 12 are positioned a plurality (here shown as three in number) of gas inlet nozzles respectively indicated as 16, 18 and 20. These nozzles are also connected to the manifold or combustion chamber (not shown) which serves as the source of hot gas.

It is to be noted that although each of the three inlet nozzles 16, 18 and 20 are arranged tangentially tothe -floor of the inlet chamber, the angle. of nozzle 16 is more acute than that of nozzle 18 and the angle of nozzle 18 is more acute than the angle of nozzle 20. The construction provides a vector force from each nozzle that is directed toward the rear of the inlet chamber 12 where it meets the curved lower end of the upstack 22.

As indicated above, even though the gas moves in a tangential direction through the nozzles themselves, since the apertures in the floor of the inlet chamber are in the plane of the floor and are round, there is a tendency for the gas to deviate somewhat from its initial direction toward the vertical. Also as indicated above, this is generally preferred since it permits more thorough entrainment of the particles which are fed into the mill through a feed inlet 24.

The finer particles are light enough to be swept into the upstack once they drop into the gaseous stream from the nozzle 20, but the wetter particles, which are heavier, hover along the inner surface of the outer wall of the elbow portion 28 due to the effect of the back eddy behind the nozzle 20. Furthermore, since they generally pass through the upper portion of the inlet chamber, the gas which reaches the recycled particles has already lost much of its heat while drying the particles in the lower portion, as a result of which, the recy cled particles are still relatively wet when they are deposited behind the nozzle 20.

The accumulated wet particles are not sufficiently dispersed to permit the heated gas flowing through the mill to dry the moisture on all their faces. As a result, the moisture at the interfaces between the particles acts like a paste or glue to agglomerate the particles into a thick mass. This mass not only builds up on the walls to restrict the passage of the gas and particles whirling through the mill but, when the mill is stopped for any reason, the mass slides down behind the nozzle where it is completely out of the path of the whirling stream and also often slides into and blocks the nozzle 20 itself. In addition, this agglomerated mass which remains within the mill is constantly subject to the heat of the flowing gas so that the heat builds up to the point where the mass melts or even deteriorates. This melted or deteriorated substance then acts to contaminate the finished product passing through the mill. Furthermore, if it is combustible, the accumulated heat may cause a fire in the mill.

In order to avoid the above, in accordance with the present invention, a deflector 30 is provided for the nozzle 20. This deflector 30, as shown in FIG. 1, is a generally cylindrical extension of the nozzle 20 into the interior of the inlet chamber 12. It acts to deflect the gaseous stream from nozzle 20 to sweep along the inner surface of the outer wall of the elbow portion 30 connecting the inlet chamber 12 to the upstack 22. This sweeps the deposited wet particles up through the upstack and through the mill where they are dispersed and dried in the desired manner. In this way, the nozzles l6 and 18 are still effective to provide the usual inflow of gases while the'last nozzle 20 acts both to sweep the elbow portion clear and to direct the flow into the upstack. Even though the use of this deflector may increase the velocity of the gas so that there is less entrainment of the particles, this is not important because by the time the particles reach this end of the chamber they have been substantially dried by the gases flowing through nozzles 14, 16 and 18.

' The deflector 28 may be attached in place by any desired means, such as pins, bolts, screws, or the like. It may also be made integral with the nozzle itself. This integral construction is shown in FIG. 2 where the 4 nozzle 50, corresponding to nozzle 20, is provided with an integral extension 52 that extends through an aperture in the floor of the chamber. This integral construction permits the entire nozzle to be removed or replaced from outside the chamber.

In FIG. 3 there is shown a modified nozzle and deflector structure wherein the nozzle 100, corresponding to nozzle 20, is provided with an arcuate deflector cap 102 which extends through an aperture or slot 104 on the floor of the inlet chamber and is provided with side flanges 106 pivotally connected at 108 to the nozzle 100. A set-screw 110 holds the cap 102 in any desired position of pivotal adjustment. The cap 102 is also provided with a slot 112 which encompasses the base portion of the nozzle when the cap is pivoted downwardly so as to provide clearance between the cap and the nozzle.

The above construction permits the angle of the deflector to be varied in accordance with the need at any particular time. For example, different materials being processed may have different sized particles which may be deposited in different areas and, therefore, require different angles of deflection.

The invention claimed is:

1. In a dryer for drying wet particles wherein there is an inlet chamber, an upstack leading from one end of said inlet chamber, a downstack leading back into the inlet chamber, a classifier section connecting the upstack and downstack, an exhaust port between the classifier section and downstack, a particle feed inlet leading into the inlet chamber, a gas inlet nozzle at the upstream end of the inlet chamber opposite to said upstack, and a plurality of tangential gas inlet nozzles leading into the floor of said inlet chamber, the improvement which comprises a deflector within said inlet chamber in alignment with the last gas inlet nozzle downstream from said upstream end, said deflector and the portion of said floor surrounding said last gas inlet nozzle defining a nozzle orifice within said inlet chamber which extends angularly from the plane of said floor at the downstream peripheral portion of said orifice to an elevated position relative to said floor at the upstream peripheral portion of said orifice.

2. The dryer of claim 1 wherein said deflector is integral with said last gas inlet nozzle.

3. The dryer of claim 1 wherein said deflector is an arcuate plate pivotally connected to said last gas inlet nozzle, and means to lock said deflector in selected positions of pivotal adjustment. 

1. In a dryer for drying wet particles wherein there is an inlet chamber, an upstack leading from one end of said inlet chamber, a downstack leading back into the inlet chamber, a classifier section connecting the upstack and downstack, an exhaust port between the classifier section and downstack, A particle feed inlet leading into the inlet chamber, a gas inlet nozzle at the upstream end of the inlet chamber opposite to said upstack, and a plurality of tangential gas inlet nozzles leading into the floor of said inlet chamber, the improvement which comprises a deflector within said inlet chamber in alignment with the last gas inlet nozzle downstream from said upstream end, said deflector and the portion of said floor surrounding said last gas inlet nozzle defining a nozzle orifice within said inlet chamber which extends angularly from the plane of said floor at the downstream peripheral portion of said orifice to an elevated position relative to said floor at the upstream peripheral portion of said orifice.
 2. The dryer of claim 1 wherein said deflector is integral with said last gas inlet nozzle.
 3. The dryer of claim 1 wherein said deflector is an arcuate plate pivotally connected to said last gas inlet nozzle, and means to lock said deflector in selected positions of pivotal adjustment. 